Visible-light driven macrocyclization of peptides: from a vinyl to an α-selenoketone motif.

We report a visible-light-driven, chemoselective macrocyclization of peptides that converts linear vinyl precursors into cyclic products bearing an α-selenoketone motif. The transformation proceeds in aqueous medium under mild conditions using a substoichiometric photocatalyst and blue LED irradiation, delivering high yields (>90%). The method is operationally simple, green, and broadly applicable to peptide macrocyclization.